Detector

In the COBAND rocket experiment，we use the multi-pixel (50 x 8 pixels) Nb/Al Superconducting Tunnel Junction (STJ) sensor with a grating to measure the energy of each infrared photon with high energy resolution (Figure 4). We measure the energy of each far-infrared photon in the energy range between 15 and 30 meV with less than 2% uncertainty using 50 pixels of STJ with a grating. By arraging it in 8 rows, we can obtain the information of 8 positions. The infrared telescope consists of a main mirror and a secondary mirror placed in 1.8K cryostat, and mirrors, the grating and the Nb/Al-STJ on the focal plane installed in 0.4K cryostat. The telescope is loaded on the top of a JAXA cosmic infrared observation rocket. The specifications of the rocket experiment and the satellite experiment are summarized in Table 1.






Fig.4．Cosmic Infrared Telescope. Nb/Al-STJ detector(left), Focal plane detector of the multi-pixel STJ with a grating (middle) and the cosmic infrared telescope installed in the refrigerator (right).




Table1.　Detectors for the rocket experiment and the satelite experiment

	Telescope diameter	Viewing angle	Detector; Number of pixels	Data acquisition period	Refrigerator
Rocket experiment	15cm	0.006°x 0.05°	Nb/Al-STJ 50 x 8	200sec	3He sorptin refrigerator 0.4K
Satellite experiment	20cm	0.1°	Hf-STJ 20 x 20	100days	ADR 0.1K




By JFY 2016, we have succeeded in produding the Nb/Al-STJ which satisfies the requirement on the leakage current ( < 0.1nA ) in the COBAND rocket experiment. We are developing a cryogenic low-noise preamplifier using FD-MOSFET made by Silicon-on-Insulator (SOI) technique to complete the far-infrared photon detector.

We are developing the Hf-STJ with much smaller energy-gap which is planned to be used for the future satellite experiment.